The long-term goal of this research is to understand the molecular events underlying eukaryotic gene expression. The genes I will investigate are the family of sequences coding for histone proteins in the sea urchin embryo. Early in embryogenesis these genes are selectively activated and then undergo switches in activity to synthesize a variety of histone variants. This research proposal intends to define, isolate and characterize histone gene variants by DNA cloning procedures and electron microscopy. Portions of the Histone H4 and Histone H1 genes will undergo DNA sequence analysis to determine nucleotide signals which may regulate their activity. Finally, the evolution of the histone gene family will be examined by DNA renaturation studies and electron microscopy to determine precisely which gene and spacer sequences have diverged.